Protective relay



April 17, 1934. G. LESCH 1,955,429

PROTECTIVE RELAY Filed Nov. 25, 1930 2 Sheets-Sheet 1 lllll I" 1 llllL Fig. 2. H513.

Inventor Guntram Lesa/1 By A Q Len Attorney April 17, 1934. LESCH 1,955,429

PROTECTIVE RELAY Filed Nov. 25, 1930 2 Sheets-Sheet 2 Inventor Guntram Lesa/1 Patented Apr. 17, 1934 PROTECTIVE RELAY Guntram Lesch, Mannheim-Feudenheim, Germany, assignor to Aktiengesellschaft Brown Boveri & Cie., Baden, Switzerland, a joint-stock company of Switzerland Application November 25,

1930, Serial No. 498,019

In Germany November 25, 1929 6 Claims.

This invention relates to protective relays and particularly to relays for selectively disconnecting portions of an electric transmission or distribution line in dependence on the impedance of the line in such manner that the line section nearest a fault point is put out of operation before unaffected portions of the line are out out.

This invention includes features which are improvements over the patent to J. Stoecklin, No. 1,873,986, issued on August 30, 1932, which is assigned to the same assignees as the present invention.

The circuit breakers connecting the several portions of an electric line are usually provided with releasing coils which open the circuit breaker when the coil is energized. Various current responsive, resistance or impedance responsive devices have already been proposed to operate or control the operation or energization of such releasing coils. The selective relays used heretofore require an element which differentiates the direction of flow of energy occurring in case of a disturbance which element may be a portion of the relay itself or may be an additional relay acting on the selective relay in such manner that the circuit breaker controlled is released upon the occurrence of an energy flow away from the source of supply. Such differentiation in the direction of energy flow is generally necessary to obtain a properly selective action.

There are however cases in which it is required that the selective relay operates in both of the possible directions of energy flow. Such cases require also that the time delay for operation of the selective relay be different in the different directions of operation. The use of two complete sets of the selective protective relays known heretofore for operation in the two directions is not economical and is often not possible due to the lack of the proper transformer connections for the double set of relays.

The present invention provides a structure capable of attaining the desired results namely differentiation in the direction of operation at different time delays by the use of different means connecting the operation initiating element and the time delay element or by the reversal of auxiliary contacts on the direction element of the selective relay. Such reversal may be obtained by connection of the relay to different voltages as by means of an auxiliary transformer or a tapped series resistance or may be obtained by the use of resistances in parallel with the current coil of the relay.

It is, therefore, among the objects of the present invention to provide a selective relay operating in dependence on the impedance of the section to be disconnected, in either direction of the flow of energy.

Another object of the invention is to provide a selective relay operating, in dependence on the impedance of the section to be disconnected in either direction of the flow of energy at a different time delay for each direction.

Objects and advantages, other than those above set forth, will be apparent from the following description when read in connection with the accompanying drawings in which Figure 1 diagrammatically illustrates a structure embodying the present invention connected with a section of a line to be protected,

Figs. 2 and 3 are diiferent modifications of one portion of the time delay element of the. selective protective relay shown in Fig. 1,

Fig. 4 diagrammatically illustrates a further modification of the time delay element of the selective relay by which proper differentiation between the two directions of energy flow may be obtained, and

Fig. 5 shows a modification of a system by which the time delay element of the relay controls the circuit breaker disconnecting the line to be protected in dependence on the direction of the flow of energy at different time delays.

Referring more particularly to the drawings by characters of reference, the reference numeral 10 designates a section of an electric line to be protected. The line section 10 may be isolated by opening a circuit breaker 11 under the influence of a spring 12 upon the retraction of a latch 13 due to the energization of a releasing coil 14 which is energized from a source of current 16 upon the bridging of a pair of contacts 17.

The contacts 1'7 are opened or bridged by a contact member 18 mounted on a lever 19 which is operated by the co-action of a reactance responsive tripping or operation initiating element and an impedance responsive or time delay element acting against a spring 21.

The tripping element includes a pair of rotatable armatures 22 and 23 mounted on a common spindle 24. Armature 22 is rotated by the action of a coil 26 on a core 27, the coil being connected with the secondary winding of a voltage transformer 28 and armature 23 is controlled by the action of a coil 31 on a core 32, the coil being supplied from a current transformer 33. The spindle 24 has mounted thereon an arm 34 which controls the engagement of a pinion 36 of a time delay mechanism 27 with a gear segment 38 mounted on and extending from the lever 19. It will thus be seen that the tripping time is dependent on the ratio of voltage to current and also on the adjustment of the time delay device 37. When the ratio of voltage to current is normal, the opposing rotating actions on the spindle will prevent engagement of the pinion and gear segments, but when a short-circuit occurs, arm 34 will be so rotated as to cause pinion 36 to engage and rotate gear egment 38 about its pivot point. Since lever 19 is pivotally attached intermediate its ends to segment 38, continued rotation of segment 38 will cause pin 49 to engage a serrated edge of plate 48. Further motion of segment 38 causes lever 19 to pivot on pin 49 and thus move contact member 18 into engagement with contacts 17 against the action of spring 21.

The impedance responsive element includes a pair of voltage coils 41 and 42 connected with the secondary winding of the voltage transformer 28 and a pair of current coils 43 and 44 connected with the current transformer 33. A spindle 47 carries vanes 45 and 46 which are magnetized by a coil to surrounding the spindle and connected in se ies with coils 44 and 45. The vane will, therefore, take a position depending on the relative magnitude and phase angles of the currents in coils 41, 42 and 44, 45; and will rotate spindle 4'? to that position. The spindle 47 carries a plate 48 having serrated edges which is arranged to move into the path or" movement or" a pin 49 on the arm 19 when the latter is rotate through an arc toward the right by the timing mechanism 37.

The serrated plate 48 is made of non-symmetrical shape as shown so that the teeth on one end are farther from the pin 49 than those oi the other end, so that the time delays for the two directions or" ilow will differ by a constant quantity. The position of the plate is dependent on the rotation of spindle 47 in either direction dependent on the direction of flow of energy in the line 10, noting that Figs. 1, 4 and 5 show plate 48 actuated to a position corresponding to a fault condition of minimum impedance. It will be seen that the time delay in the movement of contact member 18 depends on the position of plate 48 and hence on the impedance on the line 10 for the reason that the plate determines the length of the arc through which lever 19 may be moved by the timing mechanism 37 before engagement of the pin 49 therewith.

Figs. 2 and 3 illustrate other forms of the plate which may be used when diiierent time characteristics are desired. As shown in Fig. 2 the characteristics for the two directions of energy how will be different but with substantially proportional time delays while in Fig. 3 the plate is formed to give a step-by-step characteristic.

The modification shown in Fig. 4 differs from that shown in Fig. l by the use of a symmetrical plate 48 and the provision of a cam 51 on the spindle 47 which cam controls the closing of a pair of contacts 52. Contacts 52 short-circuit a variable portion of an adjustable resistance 53 connected with the voltage coils 41 and 42. The amount of resistance 53 determines the voltagecurrent ratio and hence the degree of rotation of spindle 4'7. In one direction of movement, a portion of the resistance 53 is short-circuited whereas in the opposite direction of movement, all of the resistance remains in circuit. The amount of rotation of plate 48 will thus be different dependent on the direction of rotation and the operating time of the relay will therefore be varied in the same manner.

As shown in Fig. 5, the operating time is varied in either direction of rotation by the use of a cam 54 on shaft 47 which cam closes one of the pairs of contacts 56 or 57 thereby controlling the supply of current from a source 58 to a pair of relays 61 or 62 which control the application of the source 16 to the releasing coil 14. The relay 61 is shown as being instantly operable so that, in the direction controlling such relay, energization of coil 14 depends merely on the time delay of the initiating element and the impedance responsive element whereas relay 62 is provided with a dash pot to lengthen the time of operation thereof and thereby lengthen the time elapsing before energization of the coil 14 in the opposite direction.

Although but a few embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

The invention claimed is:

1. In a protective system comprising a transmission line subject to energy flow therein in one or the opposite direction and a line switch there'- in having tripping means therefor, the combination of a switch device operable to close an energizing circuit for said tripping means, a variable time delay mechanism arranged to operate said switch device to its closed position, means for inir tiating the operation of said time delay mechanism in response to a decrease in the ratio of the voltage of said line to the current in said line be low predetermined ratio upon occurrence of a fault on said line, and means for varying the delay time of said time delay mechanism in accordance with the impedance of said line upon occurrence of a fault which causes energy to flow in said line in either said one or the opposite direction, said time delay varying means being arranged to vary the time delay differently with respect to the direction of energy flow of the same magnitude in said line.

2. In a protective system for a transmission line subject to energy flow therein in one or the opposite direction and having a line switch therein provided with tripping means, the combination of a switch device arranged to control said tripping means, a variable time delay mechanism arranged to operate said switch device, means for initiating the operation of said time delay mechanism in response to the ratio of the voltage of said line to the current in said line upon occurrence of a fault on said line which causes energy to flow in either one or the opposite direction, and means for varying the elapsed time between the initiation of the operation of said time delay mechanism and the operation of said switch device in inverse accordance with the impedance of said line upon occurrence of a fault on said line which causes energy to flow either in one or the opposite direction, said time delay varying means comprising means for causing the various elapsed tin es for an energy flow in one direction to be different with respect to the various elapsed times for energy flow in the opposite direction with equal line impedance conditions respectively.

3. In a protective system for a transmission line subject to energy flow therein in one or the opposite direction and having a line switch therein provided with tripping means, the combination of a switch device operable to effect the actuation of said tripping means, a variable time delay mechanism arranged to operate said switch device, means for initiating the operation of said time delay mechanism in response to the occurrence of a predetermined fault condition on said line which causes energy to flow in said line in one or the opposite direction, and means for automatically varying the time delay between the initiation of the operation of said time delay mechanism and the actuation of said tripping means inversely proportional to the impedance of said line upon occurrence of a fault on said line which causes energy to flow in either one or the opposite direction, said time delay varying means comprising means dependent upon the direction of energy fiow for causing said time delay to vary different amounts for one direction of energy flow with respect to the opposite direction of energy flow caused by faults of equal line impedances.

4. In a system of the character described, an electrical transmission line subject to energy flow therein in one and another direction, switching means therefor, cooperating contact members disposed for connection one with another to cause actuation of said switching means, a timing element and a time delay element operative upon conjoint actuation thereof to effect said connection of said members, an electromagnetic means connected with and operative in dependence upon the impedance of said line upon the occurrence of a fault therein for initiating movement of said timing element, a second electromagnetic means connected in circuit with and movable in one or another direction in dependence upon the direction of energy flow in said line and in dependence upon the impedence thereof upon the occurrence of a fault therein for controlling the length of time of movement of the said timing device from the moment of initiation of movement thereof to the carrying out of the same, an adjustable resistance connected in-circuit with said line and the second said electromagnetic means, and means actuated by the second said electromagnetic means upon movement thereof in one of said directions operative to vary the effective amount of said resistance to vary the extent of movement of the said timing device in dependence upon the direction of energy flow in said line.

5. In a system of the character described, an electrical transmission line subject to energy flow therein in one and another direction, switching means therefor, electromagnetic means operable to actuate the said switching means, a source of current supply for actuating said electromagnetic means, a pair of relays having different operating characteristics operable to effect the operative connection of said source of current with said electromagnetic means, a control relay comprising a timing element and a time delay element disposed to be conjointly operated to control the operative connection of said source of current with the said electromagnetic means by way of said relays, an electromagnetic means connected with said line actuated in dependence upon the impedance thereof upon the occurrence of a fault therein to initiate movement of said timing element, an electromagnetic means connected with and operable in one or another direction in dependence upon the direction of energy flow in said line and in dependence upon the impedance thereof upon the occurrence of a fault therein to actuate the said time delay element to control the time of movement of said timing element from the moment of the initiation of movement thereof to the carrying out of the same, and means actuated upon movement of the third said electromagnetic means operative to cause actuation of one of said relays upon movement of the third said electromagnetic means in one of said directions and to cause actuation of the other of said pair of relays upon the movement thereof in the other of said directions to thereby effect actuation of said switching means in times in dependence upon the direction of energy flow in said line and in dependence upon the impedance thereof upon the occurrence of a fault there- 6. In a system of the character described, an electrical circuit subject to energy flow therein in one and another direction, switch means therefor, a movable timing element for controlling said switch means, an actuating element operable upon the occurrence of fault connections in said circuit for initiating movement of said timing element, a time delay element movable in one and another direction into the path of movement of said timing element for controlling the length of time of movement during which said timing element moves from the moment of initiation of movement thereof to the carrying out of said controlling operation, and an actuating element movable in one and another direction responsive to and in dependence upon the direction of energy flow in said circuit and in extent in dependence upon the ratio of the voltage to the current of said circuit for causing said movements of said time delay element, the said time delay element being so dimensioned as to cause said timing element to effect said controlling operation in various times which are different in dependence upon the direction of movement of the last said actuating element responsive to flow of energy in said circuit of the equal magnitude respectively for various fault conditions.

GUNTRAM LESCH. 

